The present invention relates to a small hole electrical discharge machining method and a small hole electrical discharge machining apparatus.
FIG. 1 is a view showing one example of a related small hole electrical discharge machining apparatus 100. In the small hole electrical discharge machining apparatus 100, a processing vat 101 filled up with processing fluid is provided on an X-Y table 103, and a work W is fixed to a jig 105 in the processing vat.
Above the processing vat 101, a rotary spindle 109 having an electrode 107 attached thereto is provided on a machining head 111. The machining head lll is provided so as to be freely moved in a vertical direction (Z axis direction) by a servomotor Mz. Moreover, the rotary spindle 109 is set to be rotatively driven by a motor Ms fixed to the machining head.
For example, when a small hole having a diameter of 0.2 mm or less is machined in the related small hole electrical discharge machining apparatus 100, as shown in FIG. 2, a reverse discharge has been heretofore made to be generated between a rather thick electrode material 113 and a metal block 115 to form an electrode portion 117 having a fine electrode diameter d in accordance with a diameter of a hole to be machined, and the electrode portion 117 has been used as an electrode.
However, a length l of the electrode portion 117 is limited to fifth to tenth times the diameter d of the electrode portion 117 due to a factor such as buckling and vibration of the electrode portion 117 during machining. Hence, in the discharge machining in which an electrode corrodes away, there is a problem that the number of holes which can be continuously machined is small.
Moreover, in fabricating the electrode portion 117 by the reverse discharge, since corrosion of the metal block 115 cannot be completely eliminated, it is essential to confirm a finished dimension of the electrode diameter d. For confirming the dimension, the electrode 107 is detached from the rotary spindle 109, and measurement thereof by use of a microscope and the like is repeated. Thus, the electrode portion is finished in a desired dimension. Therefore, productivity in the small hole electrical discharge machining is not enhanced.
The present invention was made in order to solve the problem as described above. An object of the present invention is to provide a small hole electrical discharge machining method capable of using a thin and long stick-shaped electrode, for which fabrication of an electrode tip thereof is not required, and a small hole electrical discharge machining apparatus having high productivity.
As means for achieving the above-described subjects, the small hole electrical discharge machining method of the present invention is a method_for a small hole electrical discharge machining apparatus including an electrode holding member for holding an upper portion of a stick-shaped or pipe-shaped electrode, and an electrode guiding member for guiding a lower portion of the electrode. Moreover, the electrode holding member is provided with a jet nozzle for generating a water jet. The method is characterized in that the electrode is fed to a work while being rotated simultaneously when the electrode is guided by use of the water jet.
Moreover, a small hole electrical discharge machining apparatus of the present invention is characterized by including: a slide base; a Z axis slide freely positionable in a vertical direction, the Z axis slide being provided on the slide base; an electrode holding member for holding an upper portion of a stick-shaped or pipe-shaped electrode, the electrode holding member being provided on the Z axis slide so as to be freely rotatable; an electrode guiding member for guiding a lower portion of the electrode, the electrode guiding member being provided on the slide base; and an electrode motor for rotatively driving the electrode holding member, the electrode motor being provided on the Z axis slide. In the apparatus, the electrode holding member is provided with a jet nozzle for guiding the electrode by use of a water jet.
Moreover, in the small hole electrical discharge machining apparatus, the electrode guiding member is characterized by including: a guide unit provided with an electrode guide made of ceramics; a funnel for guiding the water jet to a center of the guide unit; and a splash preventing member for preventing splash of the water jet.